/* ecrypt-sync.h */

/*
* Header file for synchronous stream ciphers without authentication
* mechanism.
*
* *** Please only edit parts marked with "[edit]". ***
*/

#ifndef ECRYPT_SYNC
#define ECRYPT_SYNC

#if defined(__cplusplus)
extern "C" {
#endif


#include "ecrypt-portable.h"

  /* ------------------------------------------------------------------------- */

  /* Cipher parameters */

  /*
  * The name of your cipher.
  */
#define ECRYPT_NAME "ChaCha8"
#define ECRYPT_PROFILE "_____"

  /*
  * Specify which key and IV sizes are supported by your cipher. A user
  * should be able to enumerate the supported sizes by running the
  * following code:
  *
  * for (i = 0; ECRYPT_KEYSIZE(i) <= ECRYPT_MAXKEYSIZE; ++i)
  *   {
  *     keysize = ECRYPT_KEYSIZE(i);
  *
  *     ...
  *   }
  *
  * All sizes are in bits.
  */

#define ECRYPT_MAXKEYSIZE 256                 /* [edit] */
#define ECRYPT_KEYSIZE(i) (128 + (i)*128)     /* [edit] */

#define ECRYPT_MAXIVSIZE 64                   /* [edit] */
#define ECRYPT_IVSIZE(i) (64 + (i)*64)        /* [edit] */

  /* ------------------------------------------------------------------------- */

  /* Data structures */

  /*
  * ECRYPT_ctx is the structure containing the representation of the
  * internal state of your cipher.
  */

  typedef struct
  {
    u32 input[16]; /* could be compressed */
                   /*
                   * [edit]
                   *
                   * Put here all state variable needed during the encryption process.
                   */
  } ECRYPT_ctx;

  /* ------------------------------------------------------------------------- */

  /* Mandatory functions */

  /*
  * Key and message independent initialization. This function will be
  * called once when the program starts (e.g., to build expanded S-box
  * tables).
  */
  void ECRYPT_init();

  /*
  * Key setup. It is the user's responsibility to select the values of
  * keysize and ivsize from the set of supported values specified
  * above.
  */
  void ECRYPT_keysetup(
    ECRYPT_ctx* ctx,
    const u8* key,
    u32 keysize,                /* Key size in bits. */
    u32 ivsize);                /* IV size in bits. */

  /*
  * IV setup. After having called ECRYPT_keysetup(), the user is
  * allowed to call ECRYPT_ivsetup() different times in order to
  * encrypt/decrypt different messages with the same key but different
  * IV's.
  */
  void ECRYPT_ivsetup(
    ECRYPT_ctx* ctx,
    const u8* iv);

  /*
  * Encryption/decryption of arbitrary length messages.
  *
  * For efficiency reasons, the API provides two types of
  * encrypt/decrypt functions. The ECRYPT_encrypt_bytes() function
  * (declared here) encrypts byte strings of arbitrary length, while
  * the ECRYPT_encrypt_blocks() function (defined later) only accepts
  * lengths which are multiples of ECRYPT_BLOCKLENGTH.
  *
  * The user is allowed to make multiple calls to
  * ECRYPT_encrypt_blocks() to incrementally encrypt a long message,
  * but he is NOT allowed to make additional encryption calls once he
  * has called ECRYPT_encrypt_bytes() (unless he starts a new message
  * of course). For example, this sequence of calls is acceptable:
  *
  * ECRYPT_keysetup();
  *
  * ECRYPT_ivsetup();
  * ECRYPT_encrypt_blocks();
  * ECRYPT_encrypt_blocks();
  * ECRYPT_encrypt_bytes();
  *
  * ECRYPT_ivsetup();
  * ECRYPT_encrypt_blocks();
  * ECRYPT_encrypt_blocks();
  *
  * ECRYPT_ivsetup();
  * ECRYPT_encrypt_bytes();
  *
  * The following sequence is not:
  *
  * ECRYPT_keysetup();
  * ECRYPT_ivsetup();
  * ECRYPT_encrypt_blocks();
  * ECRYPT_encrypt_bytes();
  * ECRYPT_encrypt_blocks();
  */

  void ECRYPT_encrypt_bytes(
    ECRYPT_ctx* ctx,
    const u8* plaintext,
    u8* ciphertext,
    u32 msglen);                /* Message length in bytes. */

  void ECRYPT_decrypt_bytes(
    ECRYPT_ctx* ctx,
    const u8* ciphertext,
    u8* plaintext,
    u32 msglen);                /* Message length in bytes. */

  /* ------------------------------------------------------------------------- */

  /* Optional features */

  /*
  * For testing purposes it can sometimes be useful to have a function
  * which immediately generates keystream without having to provide it
  * with a zero plaintext. If your cipher cannot provide this function
  * (e.g., because it is not strictly a synchronous cipher), please
  * reset the ECRYPT_GENERATES_KEYSTREAM flag.
  */

#define ECRYPT_GENERATES_KEYSTREAM
#ifdef ECRYPT_GENERATES_KEYSTREAM

  void ECRYPT_keystream_bytes(
    ECRYPT_ctx* ctx,
    u8* keystream,
    u32 length);                /* Length of keystream in bytes. */

#endif

/* ------------------------------------------------------------------------- */

/* Optional optimizations */

/*
* By default, the functions in this section are implemented using
* calls to functions declared above. However, you might want to
* implement them differently for performance reasons.
*/

/*
* All-in-one encryption/decryption of (short) packets.
*
* The default definitions of these functions can be found in
* "ecrypt-sync.c". If you want to implement them differently, please
* undef the ECRYPT_USES_DEFAULT_ALL_IN_ONE flag.
*/
#define ECRYPT_USES_DEFAULT_ALL_IN_ONE        /* [edit] */

  void ECRYPT_encrypt_packet(
    ECRYPT_ctx* ctx,
    const u8* iv,
    const u8* plaintext,
    u8* ciphertext,
    u32 msglen);

  void ECRYPT_decrypt_packet(
    ECRYPT_ctx* ctx,
    const u8* iv,
    const u8* ciphertext,
    u8* plaintext,
    u32 msglen);

  /*
  * Encryption/decryption of blocks.
  *
  * By default, these functions are defined as macros. If you want to
  * provide a different implementation, please undef the
  * ECRYPT_USES_DEFAULT_BLOCK_MACROS flag and implement the functions
  * declared below.
  */

#define ECRYPT_BLOCKLENGTH 64                  /* [edit] */

#define ECRYPT_USES_DEFAULT_BLOCK_MACROS      /* [edit] */
#ifdef ECRYPT_USES_DEFAULT_BLOCK_MACROS

#define ECRYPT_encrypt_blocks(ctx, plaintext, ciphertext, blocks)  \
  ECRYPT_encrypt_bytes(ctx, plaintext, ciphertext,                 \
    (blocks) * ECRYPT_BLOCKLENGTH)

#define ECRYPT_decrypt_blocks(ctx, ciphertext, plaintext, blocks)  \
  ECRYPT_decrypt_bytes(ctx, ciphertext, plaintext,                 \
    (blocks) * ECRYPT_BLOCKLENGTH)

#ifdef ECRYPT_GENERATES_KEYSTREAM

#define ECRYPT_keystream_blocks(ctx, keystream, blocks)            \
  ECRYPT_keystream_bytes(ctx, keystream,                        \
    (blocks) * ECRYPT_BLOCKLENGTH)

#endif

#else

  void ECRYPT_encrypt_blocks(
    ECRYPT_ctx* ctx,
    const u8* plaintext,
    u8* ciphertext,
    u32 blocks);                /* Message length in blocks. */

  void ECRYPT_decrypt_blocks(
    ECRYPT_ctx* ctx,
    const u8* ciphertext,
    u8* plaintext,
    u32 blocks);                /* Message length in blocks. */

#ifdef ECRYPT_GENERATES_KEYSTREAM

  void ECRYPT_keystream_blocks(
    ECRYPT_ctx* ctx,
    const u8* keystream,
    u32 blocks);                /* Keystream length in blocks. */

#endif

#endif

/*
* If your cipher can be implemented in different ways, you can use
* the ECRYPT_VARIANT parameter to allow the user to choose between
* them at compile time (e.g., gcc -DECRYPT_VARIANT=3 ...). Please
* only use this possibility if you really think it could make a
* significant difference and keep the number of variants
* (ECRYPT_MAXVARIANT) as small as possible (definitely not more than
* 10). Note also that all variants should have exactly the same
* external interface (i.e., the same ECRYPT_BLOCKLENGTH, etc.).
*/
#define ECRYPT_MAXVARIANT 1                   /* [edit] */

#ifndef ECRYPT_VARIANT
#define ECRYPT_VARIANT 1
#endif

#if (ECRYPT_VARIANT > ECRYPT_MAXVARIANT)
#error this variant does not exist
#endif

/* ------------------------------------------------------------------------- */

#if defined(__cplusplus)
//extern "C" {
}
#endif

#endif